winbind wbcGetpwnam WBC_ERR_DOMAIN_NOT_FOUND

[Shirish Pargaonkar]

A call to wbcGetpwnam() with BUILTIN\Administrators
name (string) returns error 7 (WBC_ERR_DOMAIN_NOT_FOUND).

I tried just Administrators and got the same error.
Same error with user (string)  Everyone  also.

I want to call wbcUidToSid() with the correct pw_uid after
wbcGetpwnam() succeeds.

Is there another/a way I can obtain a valid SID for any
valid given name or is this expected behaviour/error?

Regards,

Shirish